46 NORTHERN FISHES 



and propagation was based on armchair biology. The use of hatcheries 

 and rearing ponds should be confined to actual needs that are proven 

 and not surmised. Hatcheries and rearing ponds are necessary to sup- 

 ply fishes needed for introduction into waters where they do not al- 

 ready occur. Small cold lakes and ponds can be rendered productive 

 by introducing trout. As alreadj' pointed out, there are many lakes 

 suitable for walleyes which have been found to contain no walleyes. 

 Some of these lakes in Cook and Lake counties have been successfully 

 stocked by the introduction of fry and are now excellent fishing lakes. 

 These are cases of introducing a species into suitable waters where 

 there is no competition of its own kind, and do not fall into the cate- 

 gory of ordinary stocking. The scarcity of northern pike in some Min- 

 nesota lakes is thought to be responsible for the overcrowding of perch 

 and pan fishes; hatcheries can be an important source of northern pike 

 to remedy this condition. 



The stocking of streams with trout differs from the stocking of 

 lakes. We shall probably always be dependent on hatcheries and rear- 

 ing ponds for a supply of fingerlings and larger sizes of brook, rainbow, 

 and brown trout to replenish the many northern trout streams. All 

 the various species of trout found in the northern states have been 

 introduced into suitable waters more or less successfully. In fact, every 

 trout in Minnesota except lake trout can claim more or less recent 

 hatchery ancestors. The combination of heavy fishing, natural losses 

 including migration into unsuitable water, and lack of suflficient spawn- 

 ing and rearing areas make it impossible to maintain satisfactory 

 trout populations in most of the northern streams. Except for these 

 special cases, natural reproduction usually furnishes more fry than the 

 body of water could possibly support. 



There is no doubt that many of our old ideas about hatcheries and 

 legal restrictions are no longer valid. We have been meddling with 

 something we knew little about. Modern investigators show that we 

 need different methods for fish conservation than those that have been 

 followed for many years. Instead of relying on artificial propagation 

 and legal restrictions, we must seek to maintain a balance between 

 natural production and our fish catches. Conservation of fishes has been 

 a slow and painful process; it is fortunate that as a group fish are 

 tough and that, with the exception of a few species such as sturgeons 

 and the paddlefish, they have done well under man's blundering at- 

 tempts to manipulate them by laws and propagation. 



